Updated 30 July 2014

High salt intake linked to higher stroke risk

Older adults with salty diets may have an increased risk of suffering a stroke, a new study suggests.

Older adults with salty diets may have an increased risk of suffering a , a new study suggests.

The new findings strengthen the case for heavy salt intake as a stroke risk factor, according to Dr Francesco P. Cappuccio, of the University of Warwick in the UK, who wrote an editorial published with the study in the Journal Stroke.

Researchers found that of close to 2 700 older, mostly minority adults, those who got well above the recommended sodium intake were nearly three times as likely to suffer a stroke over 10 years as people who met guidelines recommended by the American Heart Association (AHA).

It's well-known that as people's sodium intake goes up, their blood pressure is likely to increase as well. It's been less clear, though, whether a salty diet may ultimately mean higher risks of heart attack and stroke down the road.

Unlike blood pressure, which changes quickly, stroke and heart disease are long-range complications. So studying the relationship between people's sodium intake and their risk of heart problems and stroke is more difficult.

Managing your sodium intake

Right now, the AHA suggests that people limit their sodium intake to no more than 1 500 milligramme a day. That's a bit more strict than some other recommendations; the World Health Organization, for example, advises a limit of 2 000 milligramme.

But people in the current study – mainly black and Hispanic New Yorkers -- typically consumed well above those recommendations. They averaged 3 031 milligramme of sodium per day.

The findings are based on 2 657 adults who were interviewed about their health and lifestyle, and completed dietary questionnaires. They were 69 years old, on average, at the study's start.

Over the next 10 years, there were 235 strokes in the group. And people who'd downed at least 4 000 milligramme of sodium each day at the outset were almost three times more likely to suffer a stroke as those who'd kept their daily sodium below 1 500 milligramme. Among the 558 people whose sodium intake topped 4 000 milligramme per day, there were 66 strokes.

That compared with 24 strokes among the 320 people who met the AHA guideline.

Cause-effect unclear

"We can't definitively draw conclusions about cause-and-effect," said Hannah Gardener, a researcher at the University of Miami School of Medicine who led the study.

People who keep their salt intake in check may be healthier in a number of other ways, too, according to Gardener. Still, she and her colleagues accounted for study participants' smoking habits, exercise levels, education and health conditions that can contribute to strokes – like diabetes and high blood pressure.

And there was still a strong correlation between sodium and stroke risk, the study found. "I think our findings absolutely support the AHA recommendation," Gardener said in an interview. But right now, few Americans may be meeting that goal.

It's estimated that the typical US man gets 4 000 milligramme of sodium a day, while women typically get 2,800 milligramme.

Read the label

Since added salt is pervasive in the food supply -- from canned soups and sauces, to breads and cereals, to processed meats -- it can be challenging to cut down. Americans get almost 80% of their sodium from the prepared foods on supermarket shelves and in restaurants, rather than their own salt shakers.

"Certainly the foods popular with Americans are laden with sodium," Gardener said. "In order to adhere to the (AHA) recommendations," she noted, "you really need to read labels."

She also suggested sticking to "whole foods," like fruits, vegetables and whole grains, as much as possible. But both Gardener and Cappuccio said it shouldn't be left up to consumers alone. The food industry and public health officials should bear responsibility too, they said.

"The key is reformulation of the food chain supplied by the industry," Cappuccio said. He added that that could be done through a "voluntary" agreement where food makers pledge to meet certain "salt targets."

In the UK, the government has taken just that approach with the processed food industry (though not yet restaurants). In the US, New York City has led the way, coordinating the National Salt Reduction Initiative.

The NSRI is a coalition of local and state governments and health groups working with industry to cut sodium in packaged foods and restaurants. More than two dozen food companies, including Heinz, Kraft Foods and Starbucks, have signed on to meet certain salt targets.

Ask the Expert

Dr. Ashleigh Bhanjan is a specialist neurologist at the Life Entabeni hospital in Durban. Dr. Bhanjan completed his internship at Johannesburg General hospital and his community service at Ladysmith Provincial hospital before qualifying as a Fellow of the College of Neurologists of South Africa in 2008. Since 2009, he has been practicing at the Life Entabeni hospital as a specialist neurologist with a particular interest in stroke neurology.

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